Salt and photoresist composition containing the same

ABSTRACT

A salt represented by the formula (X): 
     
       
         
         
             
             
         
       
         
         
           
             wherein Q 1  and Q 2 , L 1  and L 2 , ring W 1 , R 5 , w, v, Z +  and W 10  are defined in the specification.

This nonprovisional application claims priority under 35 U.S.C. §119(a)on Patent Application No. 2009-262886 filed in JAPAN on Nov. 18, 2009and on Patent Application No. 2009-262887 filed in JAPAN on Nov. 18,2009, the entire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a salt and a photoresist compositioncontaining the same.

BACKGROUND OF THE INVENTION

A chemically amplified positive photoresist composition used forsemiconductor microfabrication employing a lithography process containsan acid generator comprising a compound generating an acid byirradiation.

US 2007/0122750 A1 discloses a salt represented by the followingformula:

and a photoresist composition containing the same as an acid generator.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a novel salt and aphotoresist composition containing the same.

The present invention relates to the followings:

<1> A salt represented by the formula (X):

wherein Q¹ and Q² each independently represent a fluorine atom or aC1-C6 perfluoroalkyl group, L¹ and L² independently each represent aC1-C17 divalent saturated hydrocarbon group in which one or more —CH₂—can be replaced by —O— or —CO—, ring W¹ represents a C3-C36 saturatedhydrocarbon ring, R⁵ is independently in each occurrence a C1-C6 alkylgroup or a C1-C6 alkoxy group, w represents an integer of 0 to 2, vrepresents 1 or 2, Z⁺ represents an organic counter ion, and W¹⁰representsa group represented by the formula (X-1):

wherein ring W² represents a C3-C36 saturated hydrocarbon ring, R¹represents a C1-C12 hydrocarbon group, R² is independently in eachoccurrence a C1-C6 alkyl group or a C1-C6 alkoxy group, and s representsan integer of 0 to 2, or a group represented by the formula (X-2):

wherein ring W³ represents a C4-C36 lactone ring, R³ is independently ineach occurrence a C1-C6 alkyl group, a C1-C6 alkoxy group or a C2-C7alkoxycarbonyl group and t represents an integer of 0 to 2;<2> The salt according to <1>, wherein W¹⁰ is the group represented bythe formula (X-1);<3> The salt according to <1>, wherein W¹⁰ is the group represented bythe formula (X-2);<4> The salt according to any one of <1> to <3>, wherein L¹ is *—CO—O—or *—CO—O—CH₂—CO—O— in which * represents a binding position to—C(Q¹)(Q²)-;<5> The salt according to any one of <1> to <4>, wherein L² is*—O—CH₂—CO—O— in which * represents a binding position to ring W¹;<6> The salt according to any one of <1> to <5>, wherein Z⁺ is atriarylsulfonium cation;<7> An acid generator comprising the salt according to any one of <1> to<6>;<8> A photoresist composition comprising the acid generator according to<7> and a resin comprising a structural unit having an acid-labilegroup, being insoluble or poorly soluble in an aqueous alkali solutionbut becoming soluble in an aqueous alkali solution by the action of anacid;<9> The photoresist composition according to <8>, which further containsa basic compound;<10> A process for producing a photoresist pattern comprising thefollowing steps (1) to (5):

(1) a step of applying the photoresist composition according to <8> or<9> on a substrate,

(2) a step of forming a photoresist film by conducting drying,

(3) a step of exposing the photoresist film to radiation,

(4) a step of baking the exposed photoresist film, and

(5) a step of developing the baked photoresist film with an alkalinedeveloper, thereby forming a photoresist pattern.

DESCRIPTION OF PREFERRED EMBODIMENTS

The salt of the present invention is represented by the formula (X):

wherein Q¹ and Q² each independently represent a fluorine atom or aC1-C6 perfluoroalkyl group, L¹ and L² independently each represent aC1-C17 divalent saturated hydrocarbon group in which one or more —CH₂—can be replaced by —O— or —CO—, ring W¹ represents a C3-C36 saturatedhydrocarbon ring, R⁵ is independently in each occurrence a C1-C6 alkylgroup or a C1-C6 alkoxy group, w represents an integer of 0 to 2, vrepresents 1 or 2, Z⁺ represents an organic counter ion, and W¹⁰representsa group represented by the formula (X-1):

wherein ring W² represents a C3-C36 saturated hydrocarbon ring, R¹represents a C1-C12 hydrocarbon group, R² is independently in eachoccurrence a C1-C6 alkyl group or a C1-C6 alkoxy group, and s representsan integer of 0 to 2, or a group represented by the formula (X-2):

wherein ring W³ represents a C4-C36 lactone ring, R³ is independently ineach occurrence a C1-C6 alkyl group, a C1-C6 alkoxy group or a C2-C7alkoxycarbonyl group and t represents an integer of 0 to 2 (hereinafter,simply referred to as SALT (X)).

Examples of the C1-C6 perfluoroalkyl group include a trifluoromethylgroup, a pentafluoroethyl group, a heptafluoropropyl group, anonafluorobutyl group, an undecafluoropentyl group and atridecafluorohexyl group, and a trifluoromethyl group is preferable. Q¹and Q² each independently preferably represent a fluorine atom or atrifluoromethyl group, and Q¹ and Q² are more preferably fluorine atoms.

Examples of the C1-C17 divalent saturated hydrocarbon group include aC1-C17 linear alkylene group such as a methylene group, an ethylenegroup, a propane-1,3-diyl group, a propane-1,2-diyl group, abutane-1,4-diyl group, a butane-1,3-diyl group, a pentane-1,5-diylgroup, a hexane-1,6-diyl group, a heptane-1,7-diyl group, anoctane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diylgroup, a undecane-1,11-diyl group, a dodecane-1,12-diyl group, atridecane-1,13-diyl group, a tetradecane-1,14-diyl group, apentadecane-1,15-diyl group, a hexadecane-1,16-diyl group and aheptadecane-1,17-diyl group; a C2-C17 branched alkylene group such as a1-methyl-1,3-propylene group, a 2-methyl-1,3-propylene group, a2-methyl-1,2-propylene group, a 1-methyl-1,4-butylene group, and a2-methyl-1,4-butylene group; and a group formed by combining two or moregroups among the above-mentioned groups.

One or more —CH₂— in L¹ and L² can be replaced by —O— or —CO—.

L¹ is preferably *—CO—O-L³-, *—CO—O-L⁴-O— or *—CO—O—O-L²-CO—O— whereinL³ represents a single bond or a C1-C6 alkylene group and L⁴ and L⁵independently each represent a C1-C6 alkylene group, and represents abinding position to —C(Q¹)(Q²)-. L¹ is more preferably *—CO—O-L³- or*—CO—O-L⁵-CO—O—, and still more preferably *—CO—O—, *—CO—O—OH₂— or*—CO—O—CH₂—CH₂—CO—O— and especially preferably *—CO—O—.

L² is preferably *—O-L⁵-CO—O—, *—O-L⁷-CO—O-L⁸-O—, *—CO—O-L⁹-CO—O—*—CO—O-L¹⁰-O— or *—O-L¹¹-O— wherein L⁶ to L¹¹ independently eachrepresent a C1-C6 alkylene group and * represents a binding position toring W¹. L² is more preferably *—O-L⁶-CO—O— or *—CO—O-L⁹-CO—O—, andstill more preferably *—O—CH₂—CO—O— or —CO—O—CH₂—CO—O—.

Ring W¹ represents a C3-C36 saturated hydrocarbon ring, and, in thisspecification, “saturated hydrocarbon ring” means a ring having nounsaturated bond and consisting of carbon atoms and hydrogen atoms.Examples of the saturated hydrocarbon ring include a cyclohexane ringand an adamantane ring, and an adamantane ring is preferable.

Ring W¹ has one or two hydroxyl groups, and examples of the grouprepresented by the formula:

include the followings.

Examples of the C1-C6 alkyl group represented by R⁵ include a methylgroup, an ethyl group, a propyl group, an isopropyl group, a butylgroup, a sec-butyl group, a tert-butyl group, a pentyl group and a hexylgroup, and a C1-C4 alkyl group is preferable, and a C1-C2 alkyl group ismore preferable and a methyl group is especially preferable. Examples ofthe C1-C6 alkoxy group represented by R⁵ include a methoxy group, anethoxy group, a propoxy group, an isopropoxy group, a butoxy group, asec-butoxy group, a tert-butoxy group, a pentyloxy group and a hexyloxygroup, and a C1-C4 alkoxy group is preferable, and a C1-C2 alkoxy groupis more preferable and a methoxy group is especially preferable.

In the group represented by the formula (X-1), ring W² represents aC3-C36 saturated hydrocarbon ring. Examples of the saturated hydrocarbonring include a cyclopentane ring, a cyclohexane ring and an adamantanering, and an adamantane ring is preferable.

Examples of the C1-C12 hydrocarbon group include a C1-C12 alkyl group, aC3-C12 saturated cyclic hydrocarbon group and a group formed bycombining thereof. Examples of the C1-C12 alkyl group include a methylgroup, an ethyl group, a propyl group, an isopropyl group, a butylgroup, a sec-butyl group, a tert-butyl group, a pentyl group, a hexylgroup, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutylgroup, a 1-ethylpropyl group, a 2-ethylpropyl group, a 1-methylpentylgroup, a 2-methylpentyl group, a 3-methylpentyl group, a 4-methylpentylgroup, a 1-ethylbutyl group, a 2-ethylbutyl group, a 3-ethylbutyl group,a heptyl group, an octyl group, a nonyl group, a decyl group, an undecylgroup, a 2-ethylhexyl group and a tert-octyl group. Examples of theC3-C12 saturated cyclic hydrocarbon group include a cyclobutyl group, acyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctylgroup, a cyclononyl group, a cyclodecyl group, a 1-adamantyl group, a2-adamantyl group, an isobornyl group, and the followings.

Examples of the group represented by the formula (I-B) include thefollowings:

wherein * represents a binding position to L².

Examples of the C1-C6 alkyl group represented by R² include a methylgroup, an ethyl group, a propyl group, an isopropyl group, a butylgroup, a sec-butyl group, a tert-butyl group, a pentyl group and a hexylgroup, and a C1-C4 alkyl group is preferable, and a C1-C2 alkyl group ismore preferable and a methyl group is especially preferable. Examples ofthe C1-C6 alkoxy group represented by R² include a methoxy group, anethoxy group, a propoxy group, an isopropoxy group, a butoxy group, asec-butoxy group, a tert-butoxy group, a pentyloxy group and a hexyloxygroup, and a C1-C4 alkoxy group is preferable, and a C1-C2 alkoxy groupis more preferable and a methoxy group is especially preferable.

In the group represented by the formula (X-2), ring W³ represents aC4-C36 lactone ring . The lactone ring may be monocyclic or polycyclic.Examples thereof include the followings.

Examples of the C1-C6 alkyl group represented by R³ include a methylgroup, an ethyl group, a propyl group, an isopropyl group, a butylgroup, a sec-butyl group, a tert-butyl group, a pentyl group and a hexylgroup, and a C1-C4 alkyl group is preferable, and a C1-C2 alkyl group ismore preferable and a methyl group is especially preferable. Examples ofthe C1-C6 alkoxy group represented by R³ include a methoxy group, anethoxy group, a propoxy group, an isopropoxy group, a butoxy group, asec-butoxy group, a tert-butoxy group, a pentyloxy group and a hexyloxygroup, and a C1-C4 alkoxy group is preferable, and a C1-C2 alkoxy groupis more preferable and a methoxy group is especially preferable.Examples of the C2-C7 alkoxycarbonyl group represented by R³ include amethoxycarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group,a butoxycarbonyl group, a tert-butoxycarbonyl group, a pentyloxycarbonylgroup and a hexyloxycarbonyl group, and a tert-butoxycarbonyl group ispreferable.

Examples of SALT (X) include the followings.

Examples of the counter ion represented by Z⁺ include an onium cationsuch as a sulfonium cation, an iodonium cation, an ammonium cation, abenzothiazolium cation and a phosphonium cation, and a sulfonium cationand an iodonium cation are preferable, and an arylsulfonium cation ismore preferable, and triarylsulfonium cation is especially preferable.

Preferable examples of the cation part represented by Z⁺ include thecations represented by the formulae (b2-1) to (b2-4):

wherein R^(b4), R^(b5) and R^(b6) each independently represent a C1-C30aliphatic hydrocarbon group which can have one or more substituentsselected from the group consisting of a hydroxyl group, a C1-C12 alkoxygroup and a C6-C18 aromatic hydrocarbon group, a C3-C36 saturated cyclichydrocarbon group which can have one or more substituents selected fromthe group consisting of a halogen atom, a C2-C4 acyl group and aglycidyloxy group, or a C6-C18 aromatic hydrocarbon group which can haveone or more substituents selected from the group consisting of a halogenatom, a hydroxyl group, a C1-C36 aliphatic hydrocarbon group, a C3-C36saturated cyclic hydrocarbon group or a C1-C12 alkoxy group,R^(b7) and R^(b8) are independently in each occurrence a hydroxyl group,a C1-C12 aliphatic hydrocarbon group or a C1-C12 alkoxy group, m4 and n2independently represents an integer of 0 to 5, R^(b9) and R¹⁰ eachindependently represent a C1-C36 aliphatic hydrocarbon group or a C3-C36saturated cyclic hydrocarbon group, or R^(b9) and R¹⁰ are bonded to forma C2-C11 divalent acyclic hydrocarbon group which forms a ring togetherwith the adjacent S⁺, and one or more —CH₂— in the divalent acyclichydrocarbon group may be replaced by —CO—, —O— or —S—, andR^(b11) represents a hydrogen atom, a C1-C36 aliphatic hydrocarbongroup, a C3-C36 saturated cyclic hydrocarbon group or a C6-C18 aromatichydrocarbon group, R^(b12) represents a C1-C12 aliphatic hydrocarbongroup, a C6-C18 saturated cyclic hydrocarbon group or a C6-C18 aromatichydrocarbon group and the aromatic hydrocarbon group can have one ormore substituents selected from the group consisting of a C1-C12aliphatic hydrocarbon group, a C1-C12 alkoxy group, a C3-C18 saturatedcyclic hydrocarbon group and an C2-C13 acyloxy group, or R^(b11) andR^(b12) are bonded each other to form a C1-C10 divalent acyclichydrocarbon group which forms a 2-oxocycloalkyl group together with theadjacent —CHCO—, and one or more —CH₂— in the divalent acyclichydrocarbon group may be replaced by —CO—, —O— or —S—, andR^(b13), R^(b14), R^(b15), R^(b16), R^(b17) and R^(b18) eachindependently represent a hydroxyl group, a C1-C12 aliphatic hydrocarbongroup or a C1-C12 alkoxy group, L^(b11) represents —S— or —O— and o2,p2, s2 and t2 each independently represents an integer of 0 to 5, q2 andr2 each independently represents an integer of 0 to 4, and u2 represents0 or 1.

The aliphatic hydrocarbon group represented by R^(b9) to R^(b11) haspreferably 1 to 12 carbon atoms. The saturated cyclic hydrocarbon grouprepresented by R^(b9) to R^(b11) has preferably 3 to 18 carbon atoms andmore preferably 4 to 12 carbon atoms.

Examples of the aliphatic hydrocarbon group, the saturated cyclichydrocarbon group and the aromatic hydrocarbon group include the same asdescribed above. Preferable examples of the aliphatic hydrocarbon groupinclude a methyl group, an ethyl group, a propyl group, an isopropylgroup, a butyl group, a sec-butyl group, a tert-butyl group, a pentylgroup, a hexyl group, an octyl group and a 2-ethylhexyl group.Preferable examples of the saturated cyclic hydrocarbon group include acyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexylgroup, a cycloheptyl group, a cyclodecyl group, a 2-alkyl-2-adamantylgroup, a 1-(1-adamantyl)-1-alkyl group and an isobornyl group.Preferable examples of the aromatic group include a phenyl group, a4-methylphenyl group, a 4-ethylphenyl group, a 4-tert-butylphenyl group,a 4-cyclohexylphenyl group, a 4-methoxyphenyl group, a biphenyl groupand a naphthyl group. Examples of the aliphatic hydrocarbon group havingan aromatic hydrocarbon group include a benzyl group. Examples of thealkoxy group include a methoxy group, an ethoxy group, a propoxy group,an isopropoxy group, a butoxy group, a sec-butoxy group, a tert-butoxygroup, a pentyloxy group, a hexyloxy group, a heptyloxy group, anoctyloxy group, a 2-ethylhexyloxy group, a nonyloxy group, a decyloxygroup, an undecyloxy group and a dodecyloxy group.

Examples of the C3-C12 divalent acyclic hydrocarbon group formed bybonding R^(b9) and R^(b10) include a trimethylene group, atetramethylene group and a pentamethylene group. Examples of the ringgroup formed together with the adjacent S⁺ and the divalent acyclichydrocarbon group include a thiolan-1-ium ring (tetrahydrothipheniumring), a thian-1-ium ring and a 1,4-oxathian-4-ium ring. AC3-C7 divalentacyclic hydrocarbon group is preferable.

Examples of the C1-C10 divalent acyclic hydrocarbon group formed bybonding R^(b11) and R^(b12) include a methylene group, an ethylenegroup, a trimethylene group, a tetramethylene group and a pentamethylenegroup and examples of the ring group include the followings.

Among the above-mentioned cations, preferred is the cation representedby the formula (b2-1), and more preferred is the cation represented bythe formula (b2-1-1), and especially preferred is a triphenylsulfoniumcation.

wherein R^(b19), R^(b20) and R^(b21) are independently in eachoccurrence a hydroxyl group, a C1-C36 aliphatic hydrocarbon group, aC3-C36 saturated cyclic hydrocarbon group or a C1-C12 alkoxy group, andone or more hydrogen atoms in the aliphatic hydrocarbon group can bereplaced by a hydroxyl group, a C1-C12 alkoxy group or a C6-C18 aromatichydrocarbon group, one or more hydrogen atoms of the saturated cyclichydrocarbon group can be replaced by a halogen atom, a C2-C4 acyl groupor a glycidyloxy group, and v2, w2 and x2 independently each representan integer of 0 to 5. The aliphatic hydrocarbon group preferably has 1to 12 carbon atoms, and the saturated cyclic hydrocarbon grouppreferably has 4 to 36 carbon atoms, and it is preferred that v2, w2 andx2 independently each represent 0 or 1. It is preferred that R^(b19),R^(b20) and R^(b21) are independently halogen atom (preferably afluorine atom), a hydroxyl group, a C1-C12 alkyl group or a C1-C12alkoxy group.

Examples of the cation represented by the formula (b2-1) include thefollowings.

Examples of the cation represented by the formula (b2-2) include thefollowings.

Examples of the cation represented by the formula (b2-3) include thefollowings.

Examples of the cation represented by the formula (b2-4) include thefollowings.

Examples of SALT (X) include a salt formed by combining any one of theabove-mentioned anions with any one of the above-mentioned cations.Specific examples of SALT (X) include the followings.

The process for producing SALT (X) will be illustrated.

For example, a salt represented by the formula (b1):

can be produced as Scheme 1 described below.

wherein Z⁺, Q¹, Q², W¹, R¹, R², R⁵, W², s, v and w are the same asdefined above, and X¹ and X² independently represent a halogen atom.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom, and a chlorine atom is preferable.

The compound represented by the formula (b1-c) can be produced byreacting the compound represented by the formula (b1-a) with thecompound represented by the formula (b1-b) in the presence of a catalystsuch as pyridine in a solvent such as tetrahydrofuran. The compoundrepresented by the formula (b1-e) can be produced by reacting thecompound represented by the formula (b1-c) with the compound representedby the formula (b1-d) in the presence of a catalyst such as potassiumcarbonate and potassium iodide in a solvent such asN,N-dimethylformamide. The compound represented by the formula (b1) canbe produced by reacting the compound represented by the formula (b1-e)with the compound represented by the formula (b1-f) in the presence of acatalyst such as lithium amide in a solvent such as chloroform. Thecompound represented by the formula (b1-f) can be produced according tothe method described in JP 2008-13551 A1.

A salt represented by the formula (b2):

can be produced as Scheme 2 described below.

wherein Z⁺, Q¹, Q², R¹, R², R⁵, W¹, W², s, v and w are the same asdefined above, X³ represents a halogen atom, and L³ represents a C1-C6alkylene group.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom, and a bromine atom is preferable.

The compound represented by the formula (b2-b) can be produced byreacting the compound represented by the formula (b2-a) with thecompound represented by the formula (b1-e) in the presence of a basiccatalyst such as pyridine in a solvent such as tetrahydrofuran. Thecompound represented by the formula (b2) can be produced by reacting thecompound represented by the formula (b2-b) with the compound representedby the formula (b1-f) in the presence of a catalyst such as lithiumamide in a solvent such as chloroform.

A salt represented by the formula (b3):

can be produced as Scheme 3 described below.

wherein Z⁺, Q¹, Q², W¹, R⁵, W², R¹, R², s, v, L³, X¹, X² and X³ are thesame as defined above.

The compound represented by the formula (b3-a) can be produced byreacting the compound represented by the formula (b1-a) with thecompound represented by the formula (b1-b) in the presence of a basiccatalyst such as pyridine in a solvent such as tetrahydrofuran. Thecompound represented by the formula (b3-c) can be produced by reactingthe compound represented by the formula (b1-d) with the compoundrepresented by the formula (b3-b) in the presence of a catalyst such aspotassium carbonate and potassium iodide in a solvent such asN,N-dimethylformamide. The compound represented by the formula (b3) canbe produced by reacting the compound represented by the formula (b3-c)with the compound represented by the formula (b1-f) in the presence of acatalyst such as lithium amide in a solvent such as chloroform.

A salt represented by the formula (b4):

can be produced as Scheme 4 described below.

wherein Z⁺, Q¹, Q², W¹, R⁵, W³, R³, v, w, t, X¹ and X² are the same asdefined above.

The compound represented by the formula (b4-c) can be produced byreacting the compound represented by the formula (b4-a) with thecompound represented by the formula (b1-b) in the presence of a catalystsuch as pyridine in a solvent such as tetrahydrofuran. The compoundrepresented by the formula (b4-e) can be produced by reacting thecompound represented by the formula (b4-c) with the compound representedby the formula (b4-d) in the presence of a catalyst such as potassiumcarbonate and potassium iodide in a solvent such asN,N-dimethylformamide. The compound represented by the formula (b4) canbe produced by reacting the compound represented by the formula (b4-e)with the compound represented by the formula (b4-f) in the presence of acatalyst such as sulfuric acid in a solvent such as monochlorobenzene.The compound represented by the formula (b4-f) can be produced accordingto the method described in JP 2008-127367 A1.

A salt represented by the formula (b5):

can be produced as Scheme 5 described below.

wherein Z⁺, Q¹, Q², W¹, R³, W³, R⁵, L³, X³, t, v, and w are the same asdefined above.

The compound represented by the formula (b5-b) can be produced byreacting the compound represented by the formula (b5-a) with thecompound represented by the formula (b4-e) in the presence of a basiccatalyst such as pyridine in a solvent such as tetrahydrofuran. Thecompound represented by the formula (b5) can be produced by reacting thecompound represented by the formula (b5-b) with the compound representedby the formula (b4-f) in the presence of a catalyst such as sulfuricacid in a solvent such as monochlorobenzene.

A salt represented by the formula (b6):

can be produced as Scheme 6 described below.

wherein Z⁺, Q¹, Q², W¹, R³, W³, R⁵, L³, t, v, w, X¹, X² and X³ are thesame as defined above.

The compound represented by the formula (b6-a) can be produced byreacting the compound represented by the formula (b4-a) with thecompound represented by the formula (b5-a) in the presence of a basiccatalyst such as pyridine in a solvent such as tetrahydrofuran. Thecompound represented by the formula (b6-b) can be produced by reactingthe compound represented by the formula (b6-a) with the compoundrepresented by the formula (b4-b) in the presence of a catalyst such aspotassium carbonate and potassium iodide in a solvent such asN,N-dimethylformamide. The compound represented by the formula (b6) canbe produced by reacting the compound represented by the formula (b6-c)with the compound represented by the formula (b4-f) in the presence of acatalyst such as sulfuric acid in a solvent such as monochlorobenzene.

The acid generator of the present invention comprises SALT (X). The acidgenerator of the present invention can contain two or more kinds of SALT(X). The acid generator of the present invention can contain one or moreknown acid generators in addition to SALT (X).

The amount of the acid generator is usually 0.1 to 40 parts by weightper 100 parts by weight of solid component. In this specification,“solid component” means components other than solvents in thephotoresist composition. The content of the solid component can beanalyzed with conventional means such as liquid chromatography and gaschromatography.

The resin will be illustrated below.

The resin has an acid-labile group and is insoluble or poorly soluble inan alkali aqueous solution but becomes soluble in an alkali aqueoussolution by the action of an acid. The resin has a structural unitderived from a compound having an acid-labile group, and can be producedby polymerizing one or more compounds having an acid-labile group.

In this specification, “an acid-labile group” means a group capable ofbeing eliminated by the action of an acid.

Examples of the acid-labile group include a group represented by theformula (I):

wherein R^(a1), R^(a2) and R^(a3) independently each represent analiphatic hydrocarbon group or a saturated cyclic hydrocarbon group, orR^(a1) and R^(a2) are bonded each other to form a ring together with acarbon atom to which R^(a1) and R^(a2) are bonded.

Examples of the aliphatic hydrocarbon group include a C1-C8 alkyl group.Specific examples of the C1-C8 alkyl group include a methyl group, anethyl group, a propyl group, an isopropyl group, a butyl group, a pentylgroup, a hexyl group, a heptyl group and an octyl group. The saturatedcyclic hydrocarbon group may be monocyclic or polycyclic, and examplesthereof include a monocyclic alicyclic hydrocarbon group such as aC3-C20 cycloalkyl group (e.g. a cyclopentyl group, a cyclohexyl group, amethylcyclohexyl group, a dimethylcyclohexyl group, a cycloheptyl groupand a cyclooctyl group) and a polycyclic alicyclic hydrocarbon groupsuch as a decahydronaphthyl group, an adamantyl group, a norbornylgroup, a methylnorbornyl group, and the followings:

The saturated cyclic hydrocarbon group preferably has 3 to 20 carbonatoms.

Examples of the ring formed by bonding R^(a1) and R^(a2) each otherinclude the following groups and the ring preferably has 3 to 20 carbonatoms, and the more preferably has 3 to 12 carbon atoms.

wherein R^(a3) is the same as defined above.

The group represented by the formula (1) wherein R^(a1), R^(a2) andR^(a3) independently each represent a C1-C8 alkyl group such as atert-butyl group, the group represented by the formula (1) whereinR^(a1) and R^(a2) are bonded each other to form an adamantyl ring andR^(a3) is a C1-C8 alkyl group such as a 2-alkyl-2-adamantyl group, andthe group represented by the formula (I) wherein R^(a1) and R^(a2) areC1-C8 alkyl groups and R^(a1) is an adamantyl group such as a1-(1-adamantyl)-1-alkylalkoxycarbonyl group are preferable.

The compound having an acid-labile group is preferably an acrylatemonomer having an acid-labile group in its side chain or a methacryaltemonomer having an acid-labile group in its side chain.

Preferable examples of the compound having an acid-labile group includemonomers represented by the formulae (a1-1) and (a1-2):

wherein R^(a6) and R^(a7) each independently represents a hydrogen atomor a methyl group, R^(a1) and R^(a2) each independently represents aC1-C8 aliphatic hydrocarbon group or a C3-C10 saturated cyclichydrocarbon group, L^(a1) and L^(a2) each independently represents *—O—or *—O— (CH₂)_(k1)—CO—O— in which * represents a binding position to—CO—, and k1 represents an integer of 1 to 7, m1 represents an integerof 0 to 14 and n1 represents an integer of 0 to 10.

The aliphatic hydrocarbon group preferably has 1 to 6 carbon atoms, andthe saturated cyclic hydrocarbon group preferably has 3 to 8 carbonatoms and more preferably 3 to 6 carbon atoms.

Examples of the aliphatic hydrocarbon group include a C1-C8 alkyl groupsuch as a methyl group, an ethyl group, a propyl group, an isopropylgroup, a butyl group, a tert-butyl group, a 2,2-dimethylethyl group, a1-methylpropyl group, a 2,2-dimethylpropyl group, a 1-ethylpropyl group,a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a1-propylbutyl group, a pentyl group, a 1-methylpentyl group, a hexylgroup, a 1,4-dimethylhexyl group, a heptyl group, a 1-methylheptyl groupand an octyl group. Examples of the saturated cyclic hydrocarbon groupinclude a cyclohexyl group, a methylcyclohexyl group, adimethylcyclohexyl group, a cycloheptyl group, a methylcycloheptylgroup, a norbornyl group and a methylnorbornyl group. R^(a4) ispreferably a methyl group, an ethyl group or an isopropyl group, andR^(a5) is preferably a methyl group, an ethyl group or an isopropylgroup.

L^(a1) is preferably *—O— or *—O—(CH₂)_(f1)—CO—O— in which * representsa binding position to —CO—, and f1 represents an integer of 1 to 4, andis more preferably *—O— or *—O—CH₂—CO—O—, and is especially preferably*—O—. L^(a2) is preferably *—O— or *—O— (CH₂)_(f1)—CO—O— in which *represents a binding position to —CO—, and f1 is the same as definedabove, and is more preferably *—O— or *—O—CH₂—CO—O—, and is especiallypreferably *—O—.

In the formula (a1-1), m1 is preferably an integer of 0 to 3, and ismore preferably 0 or 1. In the formula (a1-2), n1 is preferably aninteger of 0 to 3, and is more preferably 0 or 1.

Particularly when the photoresist composition contains a resin derivedfrom a monomer having a bulky structure such as a saturated cyclichydrocarbon group, the photoresist composition having excellentresolution tends to be obtained.

Examples of the monomer represented by the formula (a1-1) include thefollowings.

Among them, preferred are 2-methyl-2-adamantyl acrylate,2-methyl-2-adamantyl methacrylate, 2-ethyl-2-adamantyl acrylate,2-ethyl-2-adamantyl methacrylate, 2-isopropyl-2-adamantyl acrylate and2-isopropyl-2-adamantyl methacrylate, and more preferred are2-methyl-2-adamantyl methacrylate, 2-ethyl-2-adamantyl methacrylate, and2-isopropyl-2-adamantyl methacrylate.

Examples of the monomer represented by the formula (a1-2) include thefollowings.

Among them, preferred are 1-ethyl-1-cyclohexyl acrylate and1-ethyl-1-cyclohexyl methacrylate, and more preferred is1-ethyl-1-cyclohexyl methacrylate.

The content of the structural unit derived from a compound having anacid-labile group in the resin is usually 10 to 95% by mole, preferably15 to 90% by mole and more preferably 20 to 85% by mole based on 100% bymole of all the structural units of the resin.

Other examples of the compound having an acid-labile group include amonomer represented by the formula (a1-3):

wherein R^(a9) represents a hydrogen atom, a C1-C3 aliphatic hydrocarbongroup which can have one or more substituents, a carboxyl group, a cyanogroup or a —COOR^(a13) group in which R^(a13) represents a C1-C8aliphatic hydrocarbon group or a C3-C8 saturated cyclic hydrocarbongroup, and the C1-C8 aliphatic hydrocarbon group and the C3-C8 saturatedcyclic hydrocarbon group can have one or more hydroxyl groups, and oneor more —CH₂— in the C1-C8 aliphatic hydrocarbon group and the C3-C8saturated cyclic hydrocarbon group can be replaced by —O— or —CO—,R^(a10), R^(a11) and R^(a12) each independently respesent a C1-C12aliphatic hydrocarbon group or a C3-C12 saturated cyclic hydrocarbongroup, and R^(a10) and R^(a11) can be bonded each other to form a ringtogether with the carbon atom to which R^(a10) and R^(a11) are bonded,and the C1-C12 aliphatic hydrocarbon group and the C3-C12 saturatedcyclic hydrocarbon group can have one or more hydroxyl groups, and oneor more —CH₂— in the C1-C12 aliphatic hydrocarbon group and the C3-C12saturated cyclic hydrocarbon group can be replaced by —O— or —CO—.

Examples of the substituent include a hydroxyl group. Examples of theC1-C3 aliphatic hydrocarbon group which can have one or moresubstituents include a methyl group, an ethyl group, a propyl group, ahydroxymethyl group and a 2-hydroxyethyl group. Examples of R^(an)include a methyl group, an ethyl group, a propyl group, a2-oxo-oxolan-3-yl group and a 2-oxo-oxolan-4-yl group. Examples ofR^(a10), R^(a11) and R^(a12) include a methyl group, an ethyl group, acyclohexyl group, a methylcyclohexyl group, a hydroxycyclohexyl group,an oxocyclohexyl group and an adamantyl group, and examples of the ringformed by bonding R^(a10) and R^(a11) each other together with thecarbon atom to which R^(a10) and R^(a11) are bonded include acyclohexane ring and an adamantane ring.

Examples of the monomer represented by the formula (a1-3) includetert-butyl 5-norbornene-2-carboxylate, 1-cyclohexyl-1-methylethyl5-norbornene-2-carboxylate, 1-methylcyclohexyl5-norbornene-2-carboxylate, 2-methyl-2-adamantyl5-norbornene-2-carboxylate, 2-ethyl-2-adamantyl5-norbornene-2-carboxylate, 1-(4-methylcyclohexyl)-1-methylethyl5-norbornene-2-carboxylate, 1-(4-hydroxylcyclohexyl)-1-methylethyl5-norbornene-2-carboxylate, 1-methyl-1-(4-oxocyclohexyl)ethyl5-norbornene-2-carboxylate and 1-(1-adamantyl)-1-methylethyl5-norbornene-2-carboxylate.

When the resin has a structural unit derived from the monomerrepresented by the formula (a1-3), the photoresist composition havingexcellent resolution and higher dry-etching resistance tends to beobtained.

When the resin contains the structural unit derived form the monomerrepresented by the formula (a1-3), the content of the structural unitderived from the monomer represented by the formula (a1-3) is usually 10to 95% by mole and preferably 15 to 90% by mole and more preferably 20to 85% by mole based on total molar of all the structural units of theresin.

Other examples of the compound having an acid-labile group include amonomer represented by the formula (a1-4):

wherein R¹⁰ represents a hydrogen atom, a halogen atom, a C1-C6 alkylgroup or a C1-C6 halogenated alkyl group, R¹¹ is independently in eachoccurrence a halogen atom, a hydroxyl group, a C1-C6 alkyl group, aC1-C6 alkoxy group, a C2-C4 acyl group, a C2-C4 acyloxy group, anacryloyl group or a methacryloyl group, la represents an integer of 0 to4, R¹² and R¹³ each independently represent a hydrogen atom or a C1-C12hydrocarbon group, X^(a2) represents a single bond or a C1-C17 divalentsaturated hydrocarbon group in which one or more —CH₂— can be replacedby —O—, —CO—, —S—, —SO₂— or —N(R^(c))— wherein R^(c) represents ahydrogen atom or a C1-C6 alkyl group, and Y^(a3) represents a C1-C12aliphatic hydrocarbon group, a C3-C18 saturated cyclic hydrocarbon groupor a C6-C18 aromatic hydrocarbon group, and the C1-C12 aliphatichydrocarbon group, the C2-C18 saturated cyclic hydrocarbon group and theC6-C18 aromatic hydrocarbon group can have one or more substituents.

Examples of the halogen atom include a fluorine atom.

Examples of the C1-C6 alkyl group include a methyl group, an ethylgroup, a propyl group, an isopropyl group, a butyl group, an isobutylgroup, a sec-butyl group, a tert-butyl group, a pentyl group and a hexylgroup, and a C1-C4 alkyl group is preferable and a C1-C2 alkyl group ismore preferable and a methyl group is especially preferable.

Examples of the C1-C6 halogenated alkyl group include a trifluoromethylgroup, a pentafluoroethyl group, a heptafluoropropyl group, aheptafluoroisopropyl group, a nonafluorobutyl group, anonafluoro-sec-butyl group, a nonafluoro-tert-butyl group, aperfluoropentyl group and a perfluorohexyl group.

Examples of the C1-C6 alkoxy group include a methoxy group, an ethoxygroup, a propoxy group, an isopropoxy group, a butoxy group, anisobutoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxygroup and a hexyloxy group, and a C1-C4 alkoxy group is preferable and aC1-C2 alkoxy group is more preferable and a methoxy group is especiallypreferable.

Examples of the C2-C4 acyl group include an acetyl group, a propionylgroup and a butyryl group, and examples of the C2-C4 acyloxy groupinclude an acetyloxy group, a propionyloxy group and a butyryloxy group.

Examples of the C1-C12 hydrocarbon group include a C1-C12 aliphatichydrocarbon group such as a methyl group, an ethyl group, a propylgroup, an isopropyl group, a butyl group, an isobutyl group, a sec-butylgroup, a tert-butyl group, a pentyl group, a hexyl group, a heptylgroup, an octyl group, a 2-ethylhexyl group, a nonyl group, a decylgroup, an undecyl group and a dodecyl group, and a C3-C12 saturatedcyclic hydrocarbon group such as a cyclohexyl group, an adamantyl group,a 2-alkyl-2-adamantyl group, a 1-(1-adamantyl)-1-alkyl group and anisobornyl group.

Examples of the C1-C17 divalent saturated hydrocarbon group include aC1-C17 alkanediyl group such as a methylene group, an ethylene group, apropane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diylgroup, a hexane-1,6-diyl group, a heptane-1,7-diyl group, anoctane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diylgroup, a undecane-1,11-diyl group, a dodecane-1,12-diyl group, atridecane-1,13-diyl group, a tetradecane-1,14-diyl group, apentadecane-1,15-diyl group, a hexadecane-1,16-diyl group and aheptadecane-1,17-diyl group.

Examples of the C1-C12 aliphatic hydrocarbon group include a methylgroup, an ethyl group, a propyl group, an isopropyl group, a butylgroup, an isobutyl group, a sec-butyl group, a tert-butyl group, apentyl group, a hexyl group, a heptyl group, an octyl group, a2-ethylhexyl group, a nonyl group, a decyl group, an undecyl group and adodecyl group. Examples of the C3-C18 saturated cyclic hydrocarbon groupinclude a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, acyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononylgroup, a cyclodecyl group, a norbornyl group, a 1-adamantyl group, a2-adamantyl group, an isobornyl group and the following groups:

Examples of the C6-C18 aromatic hydrocarbon group include a phenylgroup, a naphthyl group, an anthryl group, a p-methylphenyl group, ap-tert-butylphenyl group and a p-adamantylphenyl group.

Examples of the monomer represented by the formula (a1-4) include thefollowings.

When the resin contains the structural unit derived form the monomerrepresented by the formula (a1-4), the content of the structural unitderived from the monomer represented by the formula (a1-4) is usually 10to 95% by mole and preferably 15 to 90% by mole and more preferably 20to 85% by mole based on total molar of all the structural units of theresin.

The resin can have two or more kinds of structural units derived fromthe compounds having an acid-labile group.

The resin preferably contains the structural unit derived from thecompound having an acid-labile group and a structural unit derived fromthe compound having no acid-labile group. The resin can have two or morekinds of structural units derived from the compounds having noacid-labile group. When the resin contains the structural unit derivedfrom the compound having an acid-labile group and the structural unitderived from the compound having no acid-labile group, the content ofthe structural unit derived from the compound having an acid-labilegroup is usually 10 to 80% by mole and preferably 20 to 60% by molebased on total molar of all the structural units of the resin. Thecontent of the structural unit derived from a monomer having anadamantyl group, especially the monomer represented by the formula(a1-1) in the structural unit derived from the compound having noacid-labile group is preferably 15% by mole or more from the viewpointof dry-etching resistance of the photoresist composition.

The compound having no acid-labile group preferably contains one or morehydroxyl groups or a lactone ring. When the resin contains thestructural unit derived from the compound having no acid-labile groupand having one or more hydroxyl groups or a lactone ring, a photoresistcomposition having good resolution and adhesiveness of photoresist to asubstrate tends to be obtained.

Examples of the compound having no acid-labile group and having one ormore hydroxyl groups include a monomer represented by the formula(a2-0):

wherein R⁸ represents a hydrogen atom, a halogen atom, a C1-C6 alkylgroup or a C1-C6 halogenated alkyl group, R⁹ is independently in eachoccurrence a halogen atom, a hydroxyl group, a C1-C6 alkyl group, aC1-C6 alkoxy group, a C2-C4 acyl group, a C2-C4 acyloxy group, anacryloyl group or a methacryloyl group, ma represents an integer of 0 to4, anda monomer represented by the formula (a2-1):

wherein R^(a14) represents a hydrogen atom or a methyl group, R^(a15)and R^(a16) each independently represent a hydrogen atom, a methyl groupor a hydroxyl group, L^(a1) represents *—O— or *—O—(CH₂)_(k2)—CO—O— inwhich * represents a binding position to —CO—, and k2 represents aninteger of 1 to 7, and of represents an integer of 0 to 10.

When KrF excimer laser (wavelength: 248 nm) lithography system, or ahigh energy laser such as electron beam and extreme ultraviolet is usedas an exposure system, the resin containing the structural unit derivedfrom the monomer represented by the formula (a2-0) is preferable, andwhen ArF excimer laser (wavelength: 193 nm) is used as an exposuresystem, the resin containing the structural unit derived from themonomer represented by the formula (a2-1) is preferable.

In the formula (a2-0), examples of the halogen atom include a fluorineatom, examples of the C1-C6 alkyl group include a methyl group, an ethylgroup, a propyl group, an isopropyl group, a butyl group, an isobutylgroup, a sec-butyl group, a tert-butyl group, a pentyl group and a hexylgroup, and a C1-C4 alkyl group is preferable and a C1-C2 alkyl group ismore preferable and a methyl group is especially preferable. Examples ofthe C1-C6 halogenated alkyl group include a trifluoromethyl group, apentafluoroethyl group, a heptafluoropropyl group, aheptafluoroisopropyl group, a nonafluorobutyl group, anonafluoro-sec-butyl group, a nonafluoro-tert-butyl group, aperfluoropentyl group and a perfluorohexyl group. Examples of the C1-C6alkoxy group include a methoxy group, an ethoxy group, a propoxy group,an isopropoxy group, a butoxy group, an isobutoxy group, a sec-butoxygroup, a tert-butoxy group, a pentyloxy group and a hexyloxy group, anda C1-C4 alkoxy group is preferable and a C1-C2 alkoxy group is morepreferable and a methoxy group is especially preferable. Examples of theC2-C4 acyl group include an acetyl group, a propionyl group and abutyryl group, and examples of the C2-C4 acyloxy group include anacetyloxy group, a propionyloxy group and a butyryloxy group. In theformula (a2-0), ma is preferably 0, 1 or 2, and is more preferably 0 or1, and especially preferably 0.

The resin containing the structural unit derived from the monomerrepresented by the formula (a2-0) and the structural unit derived fromthe compound having an acid generator can be produced, for example, bypolymerizing the compound having an acid generator and a monomerobtained by protecting a hydroxyl group of the monomer represented bythe formula (a2-0) with an acetyl group followed by conductingdeacetylation of the obtained polymer with a base.

Examples of the monomer represented by the formula (a2-0) include thefollowings.

Among them, preferred are 4-hydroxystyrene and4-hydroxy-α-methylstyrene.

When the resin contains the structural unit derived from the monomerrepresented by the formula (a2-0), the content of the structural unitderived from the monomer represented by the formula (a2-0) is usually 5to 90% by mole and preferably 10 to 85% by mole and more preferably 15to 80% by mole based on total molar of all the structural units of theresin.

In the formula (a2-1), R^(a14) is preferably a methyl group, R^(am) ispreferably a hydrogen atom, R^(a16) is preferably a hydrogen atom or ahydroxyl group, L^(a3) is preferably *—O— or *—O—(CH₂)_(f2)—CO—O— inwhich * represents a binding position to —CO—, and f2 represents aninteger of 1 to 4, and is more preferably *—O—, and o1 is preferably 0,1, 2 or 3 and is more preferably 0 or 1.

Examples of the monomer represented by the formula (a2-1) include thefollowings, and 3-hydroxy-1-adamantyl acrylate, 3-hydroxy-1-adamantylmethacrylate, 3,5-dihydroxy-1-adamantyl acrylate,3,5-dihydroxy-1-adamantyl methacrylate,1-(3,5-dihydroxy-1-adamantyloxycarbonyl)methyl acrylate and1-(3,5-dihydroxy-1-adamantyloxycarbonyl)methyl methacrylate arepreferable, and 3-hydroxy-1-adamantyl methacrylate and3,5-dihydroxy-1-adamantyl methacrylate are more preferable.

When the resin contains the structural unit derived from the monomerrepresented by the formula (a2-1), the content of the structural unitderived from the monomer represented by the formula (a2-1) is usually 3to 45% by mole and preferably 5 to 40% by mole and more preferably 5 to35% by mole based on total molar of all the structural units of theresin.

Examples of the lactone ring of the compound having no acid-labile groupand having a lactone ring include a monocyclic lactone ring such asβ-propiolactone ring, γ-butyrolactone ring and γ-valerolactone ring, anda condensed ring formed froma monocyclic lactone ring and the otherring. Among them, preferred are γ-butyrolactone ring and a condensedlactone ring formed from γ-butyrolactone ring and the other ring.

Preferable examples of the monomer having no acid-labile group and alactone ring include the monomers represented by the formulae (a3-1),(a3-2) and (a3-3):

wherein L^(a4), L^(a5) and L^(a6) each independently represent *—O— or*—O—(CH₂)_(k3)—CO—O— in which * represents a binding position to —CO—and k3 represents an integer of 1 to 7, R^(a18), R^(a19) and R^(a20)each independently represent a hydrogen atom or a methyl group, R^(a21)represents a C1-C4 aliphatic hydrocarbon group, R^(a22) and R^(a23) areindependently in each occurrence a carboxyl group, a cyano group or aC1-C4 aliphatic hydrocarbon group, and p1 represents an integer of 0 to5, q1 and r1 independently each represent an integer of 0 to 3.

It is preferred that L^(a4), L^(a5) and L^(a6) each independentlyrepresent *—O— or *—O—(CH₂)_(d1)—CO—O— in which * represents a bindingposition to —CO— and d1 represents an integer of 1 to 4, and it is morepreferred that L^(a4), L^(a5) and L^(a6) are *—O— R^(a18), R^(a19) andR^(a20) are preferably methyl groups. R^(a21) is preferably a methylgroup. It is preferred that R^(a22) and R^(a23) are independently ineach occurrence a carboxyl group, a cyano group or a methyl group. It ispreferred that p1 is an integer of 0 to 2, and it is more preferred thatp1 is 0 or 1. It is preferred that q1 and r1 independently eachrepresent an integer of 0 to 2, and it is more preferred that q1 and r1independently each represent 0 or 1.

Examples of the monomer represented by the formula (a3-1) include thefollowings.

Examples of the monomer represented by the formula (a3-2) include thefollowings.

Examples of the monomer represented by the formula (a3-3) include thefollowings.

Among them, preferred are 5-oxo-4-oxatricyclo[4.2.1.0^(3,7)]nonan-2-ylacrylate, 5-oxo-4-oxatricyclo[4.2.1.0^(3,7)]nonan-2-yl methacrylate,tetrahydro-2-oxo-3-furyl acrylate, tetrahydro-2-oxo-3-furylmethacrylate,2-(5-oxo-4-oxatricyclo[4.2.1.0^(3,7)]nonan-2-yloxy)-2-oxoethyl acrylateand 2-(5-oxo-4-oxatricyclo[4.2.1.0^(3,7)]nonan-2-yloxy)-2-oxoethylmethacrylate, and more preferred are5-oxo-4-oxatricyclo[4.2.1.0^(3,7)]nonan-2-yl methacrylate,tetrahydro-2-oxo-3-furyl methacrylate and2-(5-oxo-4-oxatricyclo[4.2.1.0^(3,7)]nonan-2-yloxy)-2-oxoethylmethacrylate.

When the resin contains the structural unit derived from the monomerhaving no acid-labile group and having a lactone ring, the contentthereof is usually 5 to 70% by mole and preferably 10 to 65% by mole andmore preferably 15 to 60% by mole based on total molar of all thestructural units of the resin.

The resin can contain a structural unit derived from a monomer having anacid labile group containing a lactone ring. Examples of the monomerhaving an acid labile group containing a lactone ring include thefollowings.

Examples of the other monomer having no acid-labile group include themonomers represented by the formulae (a4-1), (a4-2) and (a4-3):

wherein R^(a25) and R^(a26) each independently represents a hydrogenatom, a C1-C3 aliphatic hydrocarbon group which can have one or moresubstituents, a carboxyl group, a cyano group or a —COOR^(a27) group inwhich R^(a27) represents a C1-C36 aliphatic hydrocarbon group or aC3-C36 saturated cyclic hydrocarbon group, and one or more —CH₂— in theC1-C36 aliphatic hydrocarbon group and the C3-C36 saturated cyclichydrocarbon group can be replaced by —O— or —CO—, with the proviso thatthe carbon atom bonded to —O— of —COO— of R^(a27) is not a tertiarycarbon atom, or R^(a25) and R^(a26) are bonded together to form acarboxylic anhydride residue represented by —C(═O)OC(═O)—.

Examples of the substituent of the C1-C3 aliphatic hydrocarbon groupinclude a hydroxyl group. Examples of the C1-C3 aliphatic hydrocarbongroup which can have one or more substituents include a C1-C3 alkylgroup such as a methyl group, an ethyl group and a propyl group, and aC1-C3 hydroxyalkyl group such a hydroxymethyl group and a 2-hydroxyethylgroup. The C1-C36 aliphatic hydrocarbon group represented by R^(a27) ispreferably a C1-C8 aliphatic hydrocarbon group and is more preferably aC1-C6 aliphatic hydrocarbon group. The C3-C36 saturated cyclichydrocarbon group represented by R^(a27) is preferably a C4-C36saturated cyclic hydrocarbon group, and is more preferably C4-C12saturated cyclic hydrocarbon group. Examples of R^(a27) include a methylgroup, an ethyl group, a propyl group, a 2-oxo-oxolan-3-yl group and a2-oxo-oxolan-4-yl group.

Examples of the monomer represented by the formula (a4-3) include2-norbornene, 2-hydroxy-5-norbornene, 5-norbornene-2-carboxylic acid,methyl 5-norbornene-2-carboxylate, 2-hydroxyethyl5-norbornene-2-carboxylate, 5-norbornene-2-methanol and5-norbornene-2,3-dicarboxylic anhydride.

When the resin contains a structural unit derived from a monomerrepresented by the formula (a4-1), (a4-2) or (a4-3), the content thereofis usually 2 to 40% by mole and preferably 3 to 30% by mole and morepreferably 5 to 20% by mole based on total molar of all the structuralunits of the resin.

Preferable resin is a resin containing the structural units derived fromthe monomer having an acid-labile group, and the structural unitsderived from the monomer having one or more hydroxyl groups and/or themonomer having a lactone ring. The monomer having an acid-labile groupis preferably the monomer represented by the formula (a1-1) or themonomer represented by the formula (a1-2), and is more preferably themonomer represented by the formula (a1-1). The monomer having one ormore hydroxyl groups is preferably the monomer represented by theformula (a2-1), and the monomer having a lactone ring is preferably themonomer represented by the formula (a3-1) or (a3-2).

The resin can be produced according to known polymerization methods suchas radical polymerization.

The resin usually has 2,500 or more of the weight-average molecularweight, and preferably 3,000 or more of the weight-average molecularweight. The resin usually has 50,000 or less of the weight-averagemolecular weight, and preferably has 30,000 or less of theweight-average molecular weight. The weight-average molecular weight canbe measured with gel permeation chromatography.

The content of the resin is usually 80% by weight or more in the solidcomponent. In this specification, “solid component” means componentsother than solvents in the photoresist composition. The content of thesolid component can be analyzed with conventional means such as liquidchromatography and gas chromatography.

The photoresist composition of the present invention can contain a basiccompound as a quencher.

The basic compound is preferably a basic nitrogen-containing organiccompound, and examples thereof include an amine compound such as analiphatic amine and an aromatic amine and an ammonium salt. Examples ofthe aliphatic amine include a primary amine, a secondary amine and atertiary amine. Examples of the aromatic amine include an aromatic aminein which aromatic ring has one or more amino groups such as aniline anda heteroaromatic amine such as pyridine. Preferable examples thereofinclude an aromatic amine represented by the formula (C2):

wherein Ar^(c1) represents an aromatic hydrocarbon group, and R^(c5) andR^(c6) each independently represent a hydrogen atom, an aliphatichydrocarbon group, a saturated cyclic hydrocarbon group or an aromatichydrocarbon group, and the aliphatic hydrocarbon group, the saturatedcyclic hydrocarbon group and the aromatic hydrocarbon group can have oneor more substituents selected from the group consisting of a hydroxylgroup, an amino group, an amino group having one or two C1-C4 alkylgroups and a C1-C6 alkoxy group.

The aliphatic hydrocarbon group is preferably an alkyl group and thesaturated cyclic hydrocarbon group is preferably a cycloalkyl group. Thealiphatic hydrocarbon group preferably has 1 to 6 carbon atoms. Thesaturated cyclic hydrocarbon group preferably has 5 to 10 carbon atoms.The aromatic hydrocarbon group preferably has 6 to 10 carbon atoms.

As the aromatic amine represented by the formula (C2), an aminerepresented by the formula (C2-1):

wherein R^(c5) and R^(c6) are the same as defined above, and R^(c7) isindependently in each occurrence an aliphatic hydrocarbon group, analkoxy group, a saturated cyclic hydrocarbon group or an aromatichydrocarbon group, and the aliphatic hydrocarbon group, the alkoxygroup, the saturated cyclic hydrocarbon group and the aromatichydrocarbon group can have one or more substituents selected from thegroup consisting of a hydroxyl group, an amino group, an amino grouphaving one or two C1-C4 alkyl groups and a C1-C6 alkoxy group, and m3represents an integer of 0 to 3, is preferable. The aliphatichydrocarbon group is preferably an alkyl group and the saturated cyclichydrocarbon group is preferably a cycloalkyl group. The aliphatichydrocarbon group preferably has 1 to 6 carbon atoms. The saturatedcyclic hydrocarbon group preferably has 5 to 10 carbon atoms. Thearomatic hydrocarbon group preferably has 6 to 10 carbon atoms. Thealkoxy group preferably has 1 to 6 carbon atoms.

Examples of the aromatic amine represented by the formula (C2) include1-naphthylamine, 2-naphthylamine, aniline, diisopropylaniline,2-methylaniline, 3-methylaniline, 4-methylaniline, 4-nitroaniline,N-methylaniline, N,N-dimethylaniline, and diphenylamine, and among them,preferred is diisopropylaniline and more preferred is2,6-diisopropylaniline.

Other examples of the basic compound include amines represented by theformulae (C3) to (C11):

wherein R^(c8), R^(c20), R^(c21), and R^(c23) to R^(c28) eachindependently represent an aliphatic hydrocarbon group, an alkoxy group,a saturated cyclic hydrocarbon group or an aromatic hydrocarbon group,and the aliphatic hydrocarbon group, the alkoxy group, the saturatedcyclic hydrocarbon group and the aromatic hydrocarbon group can have oneor more substituents selected from the group consisting of a hydroxylgroup, an amino group, an amino group having one or two C1-C4 alkylgroups and a C1-C6 alkoxy group,R^(c9), R^(c10), R^(c11) to R^(c14), R^(c16) to R^(c19), and R^(c22)each independently represents a hydrogen atom, an aliphatic hydrocarbongroup, a saturated cyclic hydrocarbon group or an aromatic hydrocarbongroup, and the aliphatic hydrocarbon group, the saturated cyclichydrocarbon group and the aromatic hydrocarbon group can have one ormore substituents selected from the group consisting of a hydroxylgroup, an amino group, an amino group having one or two C1-C4 alkylgroups and a C1-C6 alkoxy group,R^(c15) is independently in each occurrence an aliphatic hydrocarbongroup, a saturated cyclic hydrocarbon group or an alkanoyl group, L^(c1)and L^(c2) each independently represents a divalent aliphatichydrocarbon group, —CO—, —C(═NH)—, —C(═NR^(c3))—, —S—, —S—S— or acombination thereof and R^(c3) represents a C1-C4 alkyl group, O3 to u3each independently represents an integer of 0 to 3 and n3 represents aninteger of 0 to 8.

The aliphatic hydrocarbon group has preferably 1 to 6 carbon atoms, andthe saturated cyclic hydrocarbon group has preferably 3 to 6 carbonatoms, and the alkanoyl group has preferably 2 to 6 carbon atoms, andthe divalent aliphatic hydrocarbon group has preferably 1 to 6 carbonatoms. The divalent aliphatic hydrocarbon group is preferably analkylene group.

Examples of the amine represented by the formula (C3) includehexylamine, heptylamine, octylamine, nonylamine, decylamine,dibutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine,dinonylamine, didecylamine, triethylamine, trimethylamine,tripropylamine, tributylamine, tripentylamine, trihexylamine,triheptylamine, trioctylamine, trinonylamine, tridecylamine,methyldibutylamine, methyldipentylamine, methyldihexylamine,methyldicyclohexylamine, methyldiheptylamine, methyldioctylamine,methyldinonylamine, methyldidecylamine, ethyldibutylamine,ethydipentylamine, ethyldihexylamine, ethydiheptylamine,ethyldioctylamine, ethyldinonylamine, ethyldidecylamine,dicyclohexylmethylamine, tris[2-(2-methoxyethoxy)ethyl]amine,triisopropanolamine, ethylenediamine, tetramethylenediamine,hexamethylenediamine, 4,4′-diamino-1,2-diphenylethane,4,4′-diamino-3,3′-dimethyldiphenylmethane and4,4′-diamino-3,3′-diethyldiphenylmethane.

Examples of the amine represented by the formula (C4) includepiperazine. Examples of the amine represented by the formula (C5)include morpholine. Examples of the amine represented by the formula(C6) include piperidine and hindered amine compounds having a piperidineskeleton as disclosed in JP 11-52575 A. Examples of the aminerepresented by the formula (C7) include 2,2′-methylenebisaniline.Examples of the amine represented by the formula (C8) include imidazoleand 4-methylimidazole. Examples of the amine represented by the formula(C9) include pyridine and 4-methylpyridine. Examples of the aminerepresented by the formula (C10) include di-2-pyridyl ketone,1,2-di(2-pyridyl)ethane, 1,2-di(4-pyridyl)ethane,1,3-di(4-pyridyl)propane, 1,2-bis(2-pyridyl)ethene,1,2-bis(4-pyridyl)ethene, 1,2-di(4-pyridyloxy)ethane, 4,4′-dipyridylsulfide, 4,4′-dipyridyl disulfide, 2,2′-dipyridylamine and2,2′-dipicolylamine. Examples of the amine represented by the formula(C11) include bipyridine.

Examples of the quaternary ammonium hydroxide includetetramethylammonium hydroxide, tetrabutylammonium hydroxide,tetrahexylammonium hydroxide, tetraoctylammonium hydroxide,phenyltrimethylammonium hydroxide,(3-trifluoromethylphenyl)trimethylammonium hydroxide and(2-hydroxyethyl)trimethylammonium hydroxide (so-called “choline”).

When the basic compound is used, the amount of the basic compound isusually 0.01 to 1 parts by weight per 100 parts by weight of solidcomponent.

The photoresist composition of the present invention usually containsone or more solvents. Examples of the solvent include a glycol etherester such as ethyl cellosolve acetate, methyl cellosolve acetate andpropylene glycol monomethyl ether acetate; a glycol ether such aspropylene glycol monomethyl ether; an acyclic ester such as ethyllactate, butyl acetate, amyl acetate and ethyl pyruvate; a ketone suchas acetone, methyl isobutyl ketone, 2-heptanone and cyclohexanone; and acyclic ester such as γ-butyrolactone.

The amount of the solvent is usually 90% by weight or more, preferably92% by weight or more preferably 94% by weight or more based on totalamount of the photoresist composition of the present invention. Theamount of the solvent is usually 99.9% by weight or less and preferably99% by weight or less based on total amount of the photoresistcomposition of the present invention.

The photoresist composition of the present invention can contain, ifnecessary, a small amount of various additives such as a sensitizer, adissolution inhibitor, other polymers, a surfactant, a stabilizer and adye as long as the effect of the present invention is not prevented.

The photoresist composition of the present invention is useful for achemically amplified photoresist composition.

A photoresist pattern can be produced by the following steps (1) to (5):

(1) a step of applying the photoresist composition of the presentinvention on a substrate,

(2) a step of forming a photoresist film by conducting drying,

(3) a step of exposing the photoresist film to radiation,

(4) a step of baking the exposed photoresist film, and

(5) a step of developing the baked photoresist film with an alkalinedeveloper, thereby forming a photoresist pattern.

The applying of the photoresist composition on a substrate is usuallyconducted using a conventional apparatus such as spin coater. Thephotoresist composition is preferably filtrated with filter having 0.2μm of a pore size before applying. Examples of the substrate include asilicon wafer or a quartz wafer on which a sensor, a circuit, atransistor or the like is formed.

The formation of the photoresist film is usually conducted using aheating apparatus such as hot plate or a decompressor, and the heatingtemperature is usually 50 to 200° C., and the operation pressure isusually 1 to 1.0*10⁵ Pa.

The photoresist film obtained is exposed to radiation using an exposuresystem. The exposure is usually conducted through a mask having apattern corresponding to the desired photoresist pattern. Examples ofthe exposure source include a light source radiating laser light in aUV-region such as a KrF excimer laser (wavelength: 248 nm), an ArFexcimer laser (wavelength: 193 nm) and a F₂ laser (wavelength: 157 nm),and a light source radiating harmonic laser light in a far UV region ora vacuum UV region by wavelength conversion of laser light from a solidlaser light source (such as YAG or semiconductor laser).

The temperature of baking of the exposed photoresist film is usually 50to 200° C., and preferably 70 to 150° C.

The development of the baked photoresist film is usually carried outusing a development apparatus. The alkaline developer used may be anyone of various alkaline aqueous solution used in the art. Generally, anaqueous solution of tetramethylammonium hydroxide or(2-hydroxyethyl)trimethylammonium hydroxide (commonly known as“choline”) is often used. After development, the photoresist patternformed is preferably washed with ultrapure water, and the remained wateron the photoresist pattern and the substrate is preferably removed.

The photoresist composition of the present invention is suitable for ArFexcimer laser lithography, KrF excimer laser lithography, ArF immersionlithography, EUV (extreme ultraviolet) lithography, EUV immersionlithography and EB (electron beam) lithography. Further, the photoresistcomposition of the present invention can especially be used for ArFimmersion lithography, EUV lithography and ER lithography. Furthermore,the photoresist composition of the present invention can also be used indouble imaging.

EXAMPLES

The present invention will be described more specifically by Examples,which are not construed to limit the scope of the present invention.

The “%” and “part(s)” used to represent the content of any component andthe amount of any material used in the following examples andcomparative examples are on a weight basis unless otherwise specificallynoted. The weight-average molecular weight of any material used in thefollowing examples is a value found by gel permeation chromatography[HLC-8120GPC Type, Column (Three Columns with guard column): TSKgelMultipore HXL-M, manufactured by TOSOH CORPORATION, Solvent:Tetrahydrofuran, Flow rate: 1.0 mL/min., Detector: RI detector, Columntemperature: 40° C., Injection volume: 100 μL] using standardpolystyrene as a standard reference material. Mass spectrometry (LiquidChromatography: 1100 Type, manufactured by AGILENT TECHNOLOGIES LTD.,Mass Spectrometry: LC/MSD Type or LC/MSD TOF Type, manufactured byAGILENT TECHNOLOGIES LTD.).

Example 1

A mixture of 27.11 parts of 2-ethyl-2-adamantanol and 200 parts oftetrahydrofuran was stirred at room temperature. To the mixture, 14.27part of pyridine was added, and the resultant mixture was heated up to40° C. To the mixture, a solution prepared by dissolving 25.47 parts ofchloroacetyl chloride in 50 parts of tetrahydrofuran was added dropwiseover 1 hour. The resultant mixture was stirred at 40° C. for 8 hours.The obtained mixture was cooled down to 5° C., and then, 100 parts ofion-exchanged water at 5° C. was added thereto followed by conductingseparation. The obtained aqueous layer was extracted with 65 parts ofethyl acetate, and the organic layer obtained was washed with 65 partsof aqueous 10% potassium carbonate solution at 5° C. The organic layerobtained was washed three times with 65 parts of ion-exchanged water.The obtained organic layer was concentrated and the residue obtained wasmixed with 50 parts of heptane, and then, the resultant mixture wasstirred and filtrated to obtain solids. The obtained solids were driedto obtain 18.98 parts of a compound represented by the formula (B1-a).

A mixture of 5.12 parts of a compound represented by the formula (B1-a)and 25 parts of N,N-dimethylformamide was stirred at 23° C. for 30minutes. To the mixture, 1.66 parts of potassium carbonate and 0.84 partof potassium iodide were added and the resultant mixture was stirred at50° C. for 1 hour. The obtained mixture was cooled down to 40° C. To themixture, a solution prepared by dissolving 3.68 parts of1,3,5-adamantanetriol in 25 parts of N,N-dimethylformamide was addeddropwise over 1 hour. The resultant mixture was stirred at 75° C. for 5hours. The obtained mixture was cooled down to 23° C., and 60 parts ofchloroform and 60 parts of 1N hydrochloric acid were added thereto toconduct separation. The organic layer obtained was repeated to wash with60 parts of ion-exchanged water until the aqueous layer was neutralized.The obtained organic layer was concentrated and the obtained residue waspurified with silica gel column chromatography (silica gel: silica gel60-200 mesh available from Merck KGaA, solvent: ethyl acetate) to obtain3.19 parts of a compound represented by the formula (B1-b).

A salt represented by the formula (B1-c) was prepared according to themethod described in JP 2008-13551 A1. A mixture of 4.52 parts of thesalt represented by the formula (B1-c), 30 parts of chloroform, 4.85parts of a compound represented by the formula (B1-b), 5 parts ofmolecular sieves (Molecular Sieves 5A available from Wako Pure ChemicalIndustries, Ltd.) and 0.14 part of lithium amide was refluxed at 80° C.for 24 hours. The reaction mixture obtained was filtrated, and to theobtained filtrate, 0.28 part of oxalic acid and 7.5 parts ofion-exchanged water were added followed by conducting separation. Theobtained organic layer was washed six times with ion-exchanged water. Tothe organic layer, 1 parts of active carbon was added to stir at 23° C.for 30 minutes followed by filtration. The filtrate obtained wasconcentrated, and to the residue obtained, 7 parts of acetonitrile wasadded to prepare a solution. The obtained solution was concentrated, and10 parts of ethyl acetate was added to the obtained residue. Theresultant mixture was stirred and then, the supernatant solution wasremoved from the mixture. To the obtained residue, 10 parts oftert-butyl methyl ether was added to the obtained residue. The resultantmixture was stirred and then, the supernatant solution was removed fromthe mixture. The obtained residue was dissolved in chloroform, and theobtained solution was concentrated to obtain 0.19 part of a saltrepresented by the formula (B1) in the form of oil. This is called asSalt B1.

MS (ESI(+) Spectrum): M⁺ 263.1

MS (ESI(−) Spectrum): M⁻ 561.2

Example 2

A mixture of 4.95 parts of the salt represented by the formula (B2-c),30 parts of chloroform, 4.85 parts of a compound represented by theformula (B1-b), 5 parts of molecular sieves (Molecular Sieves 5Aavailable from Wako Pure Chemical Industries, Ltd.) and 0.14 part oflithium amide was refluxed at 80° C. for 24 hours. The reaction mixtureobtained was filtrated, and to the obtained filtrate, 0.28 part ofoxalic acid and 7.5 parts of ion-exchanged water were added followed byconducting separation. The obtained organic layer was washed six timeswith ion-exchanged water. To the organic layer, 1 parts of active carbonwas added to stir at 23° C. for 30 minutes followed by filtration. Thefiltrate obtained was concentrated, and to the residue obtained, 10parts of acetonitrile was added to prepare a solution. The obtainedsolution was concentrated, and 10 parts of ethyl acetate was added tothe obtained residue. The resultant mixture was stirred and then, thesupernatant solution was removed from the mixture. To the obtainedresidue, 10 parts of tert-butyl methyl ether was added to the obtainedresidue. The resultant mixture was stirred and then, the supernatantsolution was removed from the mixture. The obtained residue wasdissolved in chloroform, and the obtained solution was concentrated toobtain 0.39 part of a salt represented by the formula (B2). This iscalled as Salt B2.

MS (ESI(+) Spectrum): M⁺ 305.1

MS (ESI(−) Spectrum): M⁻ 561.2

Example 3

A mixture of 4.70 parts of the salt represented by the formula (B3-c),30 parts of chloroform, 4.85 parts of a compound represented by theformula (B1-d), 5 parts of molecular sieves (Molecular Sieves 5Aavailable from Wako Pure Chemical Industries, Ltd.) and 0.14 part oflithium amide was refluxed at 80° C. for 24 hours. The reaction mixtureobtained was filtrated, and to the obtained filtrate, 0.28 part ofoxalic acid and 7.5 parts of ion-exchanged water were added followed byconducting separation. The obtained organic layer was washed six timeswith ion-exchanged water. To the organic layer, 1 parts of active carbonwas added to stir at 23° C. for 30 minutes followed by filtration. Thefiltrate obtained was concentrated, and to the residue obtained, 10parts of acetonitrile was added to prepare a solution. The obtainedsolution was concentrated, and 10 parts of ethyl acetate was added tothe obtained residue. The resultant mixture was stirred and then, thesupernatant solution was removed from the mixture. To the obtainedresidue, 10 parts of tert-butyl methyl ether was added to the obtainedresidue. The resultant mixture was stirred and then, the supernatantsolution was removed from the mixture. The obtained residue wasdissolved in chloroform, and the obtained solution was concentrated. Theobtained residue was purified with silica gel column chromatography(silica gel: silica gel 60-200 mesh available from Merck KGaA, solvent:chloroform/methanol=5/1) to obtain 0.28 part of a salt represented bythe formula (B3). This is called as Salt B3.

MS (ESI(+) Spectrum): M⁺ 281.0

MS (ESI(−) Spectrum): M⁻ 561.2

Example 4

A mixture of 3.96 parts of the salt represented by the formula (B4-c),30 parts of chloroform, 4.85 parts of a compound represented by theformula (B1-b), 5 parts of molecular sieves (Molecular Sieves 5Aavailable from Wako Pure Chemical Industries, Ltd.) and 0.14 part oflithium amide was refluxed at 80° C. for 24 hours. The reaction mixtureobtained was filtrated, and to the obtained filtrate, 0.28 part ofoxalic acid and 7.5 parts of ion-exchanged water were added followed byconducting separation. The obtained organic layer was washed six timeswith ion-exchanged water. To the organic layer, 1 parts of active carbonwas added to stir at 23° C. for 30 minutes followed by filtration. Thefiltrate obtained was concentrated, and to the residue obtained, 10parts of acetonitrile was added to prepare a solution. The obtainedsolution was concentrated, and 10 parts of ethyl acetate was added tothe obtained residue. The resultant mixture was stirred and then, thesupernatant solution was removed from the mixture. To the obtainedresidue, 10 parts of tert-butyl methyl ether was added to the obtainedresidue. The resultant mixture was stirred and then, the supernatantsolution was removed from the mixture. The obtained residue wasdissolved in chloroform, and the obtained solution was concentrated. Theresidue obtained was purified with silica gel column chromatography(silica gel: silica gel 60-200 mesh available from Merck KGaA, solvent:chloroform/methanol=5/1) to obtain 0.20 part of a salt represented bythe formula (B4). This is called as Salt B4.

MS (ESI(+) Spectrum): M⁺ 207.1

MS (ESI(−) Spectrum): M⁻ 561.2

Example 5

A mixture of 6.08 parts of a compound represented by the formula (B1-b)and 20 parts of tetrahydrofuran was stirred at room temperature. To themixture, 1.43 parts of pyridine was added, and the resultant mixture washeated up to 40° C. To the mixture, a solution prepared by dissolving2.55 parts of chloroacetyl chloride in 5 parts of tetrahydrofuran wasadded dropwise over 1 hour. The resultant mixture was stirred at 40° C.for 5 hours. The obtained mixture was cooled down to 5° C., and then, 10parts of ion-exchanged water at 5° C. and 40 parts of ethyl acetate wereadded thereto followed by conducting separation. The obtained aqueouslayer was washed with 10 parts of aqueous 10% potassium carbonatesolution at 5° C. The organic layer obtained was washed five times with10 parts of ion-exchanged water. The obtained organic layer wasconcentrated and the residue was purified with silica gel columnchromatography (silica gel: silica gel 60-200 mesh available from MerckKGaA, solvent: heptane/ethyl acetate=1/3 (volume ratio)) to obtain 2.65parts of a compound represented by the formula (B5-a).

A mixture of 2.13 parts of the compound represented by the formula(B5-b) and 11.01 parts of N,N-dimethylformamide was stirred at 23° C.for 30 minutes. To the mixture, 0.67 part of porassium carbonate and0.20 part of potassium iodide were added, and the resultant mixture wasstirred at 23° C. for 1 hour. To the mixture, a solution prepared bydissolving 1.95 parts of the compound represented by the formula (B5-a)in 3.95 parts of N,N-dimethylformamide was added dropwise over 1 hour,and then, the resultant mixture was stirred at 40° C. for 6 hours. Theobtained mixture was cooled down to 23° C., and then, 79.74 parts ofchloroform, 12.25 parts of aqueous 5% oxalic acid solution and 7.68parts of ion-exchanged water were added thereto followed by conductingseparation. The obtained organic layer was washed seven times with 31.89parts of ion-exchanged water. To the organic layer, 1 parts of activecarbon was added to stir at 23° C. for 30 minutes followed byfiltration. The filtrate obtained was concentrated, and to the residueobtained, 10 parts of acetonitrile was added to prepare a solution. Theobtained solution was concentrated, and 10 parts of ethyl acetate wasadded to the obtained residue. The resultant mixture was stirred andthen, the supernatant solution was removed from the mixture. To theobtained residue, 10 parts of tert-butyl methyl ether was added to theobtained residue. The resultant mixture was stirred and then, thesupernatant solution was removed from the mixture. The obtained residuewas dissolved in chloroform, and the obtained solution was concentrated.The residue obtained was purified with silica gel column chromatography(silica gel: silica gel 60-200 mesh available from Merck KGaA, solvent:chloroform/methanol=5/1) to obtain 1.86 parts of a salt represented bythe formula (B5). This is called as Salt B5.

MS (ESI(+) Spectrum): M⁺ 263.1

MS (ESI(−) Spectrum): M⁻ 619.2

Example 6

A mixture of 4.61 parts of a compound represented by the formula (B6-a)which is available from KURARAY CO., LTD and of which commodity name isCANL, and 25 parts of N,N-dimethylformamide was stirred at 23° C. for 30minutes. To the mixture, 1.66 parts of potassium carbonate and 0.84 partof potassium iodide were added and the resultant mixture was stirred at50° C. for 1 hour. The obtained mixture was cooled down to 40° C., and asolution prepared by dissolving 3.68 parts of 1,3,5-adamantanetriol in25 parts of N,N-dimethylformamide was added dropwise over 1 hour. Theresultant mixture was stirred at 75° C. for 5 hours. The obtainedmixture was cooled down to 23° C., and 60 parts of chloroform and 60parts of 1N hydrochloric acid were added thereto to conduct separation.The organic layer obtained was repeated to wash with 60 parts ofion-exchanged water until the obtained aqueous layer was neutralized.The obtained organic layer was concentrated and the residue obtained waspurified with silica gel column chromatography (silica gel: silica gel60-200 mesh available from Merck KGaA, solvent: ethyl acetate) to obtain2.83 parts of a compound represented by the formula (B6-b).

A salt represented by the formula (B6-c) was prepared according to themethod described in Examples 1 of JP 2008-127367 A1. A mixture of 2.19parts of the salt represented by the formula (B6-c), 30 parts ofmonochlorobenzene and 2.08 parts of a compound represented by theformula (B6-b) was stirred at 23° C. for 30 minutes. To the mixture,0.10 part of sulfuric acid and 10 parts of molecular sieves (MolecularSieves 4A available from Wako Pure Chemical Industries, Ltd.) wereadded, and the resultant mixture was refluxed at 130° C. for 3 hours toconduct dehydration. The reaction mixture obtained was concentrated toobtain a residue and to the residue, 50 parts of chloroform and 25 partsof ion-exchanged water to conduct separation. The obtained organic layerwas washed four times with ion-exchanged water. To the organic layer, 1parts of active carbon was added to stir at 23° C. for 30 minutesfollowed by filtration. The filtrate obtained was concentrated, and tothe residue obtained, 10 parts of acetonitrile was added to prepare asolution. The obtained solution was concentrated, and 10 parts of ethylacetate was added to the obtained residue. The resultant mixture wasstirred and then, the supernatant solution was removed from the mixture.To the obtained residue, 10 parts of tert-butyl methyl ether was addedto the obtained residue. The resultant mixture was stirred and then, thesupernatant solution was removed from the mixture. The obtained residuewas dissolved in chloroform, and the obtained solution was concentratedto obtain 1.12 parts of a salt represented by the formula (B6) in theform of oil. This is called as Salt B6.

MS (ESI(+) Spectrum): M⁺ 263.1

MS (ESI(−) Spectrum): M⁻ 535.1

Example 7

A mixture of 2.40 parts of a salt represented by the formula (B7-c), 30parts of monochlorobenzene and 2.08 parts of a compound represented bythe formula (B6-b) was stirred at 23° C. for 30 minutes. To the obtainedmixture, 0.1 part of sulfuric acid and 10 parts of molecular sieves(Molecular Sieves 4A available from Wako Pure Chemical Industries, Ltd.)were added thereto. The obtained mixture was refluxed at 130° C. for 3hours to conduct dehydration. The obtained mixture was concentrated, and25 parts of ion-exchanged water and 50 parts of chloroform were addedthereto to conduct separation. The organic layer obtained was washedfour times with ion-exchanged water, and then, 1 parts of active carbonwas added thereto to stir at 23° C. for 30 minutes followed byfiltration. The filtrate obtained was concentrated, and to the residueobtained, 10 parts of acetonitrile was added to prepare a solution. Theobtained solution was concentrated, and 10 parts of ethyl acetate wasadded to the obtained residue. The resultant mixture was stirred andthen, the supernatant solution was removed from the mixture. To theobtained residue, 10 parts of tert-butyl methyl ether was added. Theresultant mixture was stirred and then, the supernatant solution wasremoved from the mixture. The obtained residue was dissolved inchloroform, and the obtained solution was concentrated to obtain 1.27parts of a salt represented by the formula (B7). This is called as SaltB7.

MS (ESI(+) Spectrum): M⁺ 305.1

MS (ESI(−) Spectrum): M⁻ 535.1

Example 8

A mixture of 2.28 parts of a salt represented by the formula (B8-c), 30parts of monochlorobenzene and 2.08 parts of a compound represented bythe formula (B6-b) was stirred at 23° C. for 30 minutes. To the obtainedmixture, 0.1 part of sulfuric acid and 10 parts of molecular sieves(Molecular Sieves 4A available from Wako Pure Chemical Industries, Ltd.)were added thereto. The obtained mixture was refluxed at 130° C. for 3hours to conduct dehydration. The obtained mixture was concentrated, and25 parts of ion-exchanged water and 50 parts of chloroform were addedthereto to conduct separation. The organic layer obtained was washedfour times with ion-exchanged water, and then, 1 parts of active carbonwas added thereto to stir at 23° C. for 30 minutes followed byfiltration. The filtrate obtained was concentrated, and to the residueobtained, 10 parts of acetonitrile was added to prepare a solution. Theobtained solution was concentrated, and 10 parts of ethyl acetate wasadded to the obtained residue. The resultant mixture was stirred andthen, the supernatant solution was removed from the mixture. To theobtained residue, 10 parts of tert-butyl methyl ether was added. Theresultant mixture was stirred and then, the supernatant solution wasremoved from the mixture. The obtained residue was dissolved inchloroform, and the obtained solution was concentrated to obtain aresidue. The residue obtained was purified with silica gel columnchromatography (silica gel: silica gel 60-200 mesh available from MerckKGaA, solvent: chloroform/methanol=5/1) to obtain 0.98 part of a saltrepresented by the formula (B8). This is called as Salt B8.

MS (ESI(+) Spectrum): M⁺ 281.0

MS (ESI(−) Spectrum): M⁻ 535.1

Example 9

A mixture of 1.91 parts of a salt represented by the formula (B9-c), 30parts of monochlorobenzene and 2.08 parts of a compound represented bythe formula (B6-b) was stirred at 23° C. for 30 minutes. To the obtainedmixture, 0.1 part of sulfuric acid and 10 parts of molecular sieves(Molecular Sieves 4A available from Wako Pure Chemical Industries, Ltd.)were added thereto. The obtained mixture was refluxed at 130° C. for 3hours to conduct dehydration. The obtained mixture was concentrated, and25 parts of ion-exchanged water and 50 parts of chloroform were addedthereto to conduct separation. The organic layer obtained was washedfour times with ion-exchanged water, and then, 1 parts of active carbonwas added thereto to stir at 23° C. for 30 minutes followed byfiltration. The filtrate obtained was concentrated, and to the residueobtained, 10 parts of acetonitrile was added to prepare a solution. Theobtained solution was concentrated, and 10 parts of ethyl acetate wasadded to the obtained residue. The resultant mixture was stirred andthen, the supernatant solution was removed from the mixture. To theobtained residue, 10 parts of tert-butyl methyl ether was added. Theresultant mixture was stirred and then, the supernatant solution wasremoved from the mixture. The obtained residue was dissolved inchloroform, and the obtained solution was concentrated to obtain aresidue. The residue obtained was purified with silica gel columnchromatography (silica gel: silica gel 60-200 mesh available from MerckKGaA, solvent: chloroform/methanol=5/1) to obtain 0.66 part of a saltrepresented by the formula (B9). This is called as Salt B9.

MS (ESI(+) Spectrum): M⁺ 207.1

MS (ESI(−) Spectrum): M⁻ 535.1

Example 10

A mixture of 5.69 parts of a compound represented by the formula (B6-b)and 20 parts of tetrahydrofuran was stirred at room temperature. To themixture, 1.43 parts of pyridine was added, and the resultant mixture washeated up to 40° C. To the mixture, a solution prepared by dissolving2.55 parts of chloroacetyl chloride in 5 parts of tetrahydrofuran wasadded dropwise over 1 hour. The resultant mixture was stirred at 40° C.for 5 hours. The obtained mixture was cooled down to 5° C., and then, 10parts of ion-exchanged water at 5° C. and 40 parts of ethyl acetate wereadded thereto followed by conducting separation. The obtained aqueouslayer was washed with 10 parts of aqueous 10% potassium carbonatesolution at 5° C. The organic layer obtained was washed five times with10 parts of ion-exchanged water. The obtained organic layer wasconcentrated and the residue was purified with silica gel columnchromatography (silica gel: silica gel 60-200 mesh available from MerckKGaA, solvent: ethyl acetate) to obtain 2.22 parts of a compoundrepresented by the formula (B10-a).

A mixture of 2.50 parts of the compound represented by the formula(B10-b) and 12.96 parts of N,N-dimethylformamide was stirred at 23° C.for 30 minutes. To the mixture, 0.79 part of porassium carbonate and0.24 part of potassium iodide were added, and the resultant mixture wasstirred at 40° C. for 1 hour. To the mixture, a solution prepared bydissolving 2.16 parts of the compound represented by the formula (B10-a)in 4.38 parts of N,N-dimethylformamide was added dropwise over 1 hour,and then, the resultant mixture was stirred at 40° C. for 6 hours. Theobtained mixture was cooled down to 23° C., and then, 92.09 parts ofchloroform, 14.38 parts of aqueous 5% oxalic acid solution and 8.64parts of ion-exchanged water were added thereto followed by conductingseparation. The obtained organic layer was washed seven times with 36.83parts of ion-exchanged water. To the organic layer, 1 parts of activecarbon was added to stir at 23° C. for 30 minutes followed byfiltration. The filtrate obtained was concentrated, and to the residueobtained, 10 parts of acetonitrile was added to prepare a solution. Theobtained solution was concentrated, and 10 parts of ethyl acetate wasadded to the obtained residue. The resultant mixture was stirred andthen, the supernatant solution was removed from the mixture. To theobtained residue, 10 parts of tert-butyl methyl ether was added to theobtained residue. The resultant mixture was stirred and then, thesupernatant solution was removed from the mixture. The obtained residuewas dissolved in chloroform, and the obtained solution was concentrated.The residue obtained was purified with silica gel column chromatography(silica gel: silica gel 60-200 mesh available from Merck KGaA, solvent:chloroform/methanol=5/1) to obtain 0.61 part of a salt represented bythe formula (B10). This is called as Salt B10.

MS (ESI(+) Spectrum): M⁺263.1

MS (ESI(−) Spectrum): M⁻ 593.1

Monomers used in the following Resin Synthesis Example 1 are followingmonomers E, F, B, C and D.

Resin Synthesis Example 1

The monomers E, E, B, C and D were mixed in a molar ratio of30/14/6/20/30 (monomer E/monomer F/monomer B/monomer C/monomer D), and1,4-dioxane in 1.5 times part based on total parts of all monomers wasadded to prepare a mixture. To the mixture, azobisisobutyronitrile as aninitiator in a ratio of 1 mol % based on all monomer molar amount andazobis(2,4-dimethylvaleronitrile) as an initiator in a ratio of 3 mol %based on all monomer molar amount were added, and the obtained mixturewas heated at 73° C. for about 5 hours. The reaction mixture obtainedwas poured into a mixture of a large amount of methanol and water (4/1)to cause precipitation, and this operation was repeated three times forpurification. As a result, a resin having a weight-average molecularweight of about 8.1×10³ was obtained in a yield of 65%. This resin iscalled as resin A1.

Monomers used in the following Resin Synthesis Example 2 are followingmonomers A, B and C.

Resin Synthesis Example 2

The monomers A, B and C were mixed in a molar ratio of 50/25/25 (monomerA/monomer B/monomer C), and 1,4-dioxane in 1.5 times part based on totalparts of all monomers was added to prepare a mixture. To the mixture,azobisisobutyronitrile as an initiator in a ratio of 1 mol % based onall monomer molar amount and azobis(2,4-dimethylvaleronitrile) as aninitiator in a ratio of 3 mol % based on all monomer molar amount wereadded, and the obtained mixture was heated at 77° C. for about 5 hours.The reaction mixture obtained was poured into a mixture of a largeamount of methanol and water to cause precipitation, and this operationwas repeated three times for purification. As a result, a resin having aweight-average molecular weight of about 8.0×10³ was obtained in a yieldof 60%. This resin is called as resin A2.

Examples 11 to 16 and Comparative Example 1

<Resin>

Resin A1, A2

<Acid Generator>

Salt B1, B2, B3, B4, B5

H1:

<Quencher>C1: 2,6-diisopropylaniline<Solvent>

Y1: propylene glycol monomethyl ether acetate 265 parts propylene glycolmonomethyl ether 20 parts 2-heptanone 20 parts γ-butyrolactone 3.5 parts

The following components were mixed and dissolved, further, filtratedthrough a fluorine resin filter having pore diameter of 0.2 μm, toprepare photoresist compositions.

Resin (kind and amount are described in Table 1)

Acid Generator (kind and amount are described in Table 1)

Quencher (kind and amount are described in Table 1)

Solvent Y1

TABLE 1 Acid Resin Generator Quencher (kind/ (kind/ (kind/ amount amountamount PB PEB Ex. No. (part)) (part)) (part) ) (° C.) (° C.) Ex. 11A1/10 B1/0.7 C1/0.075 100 100 Ex. 12 A2/10 B1/0.7 C1/0.075 110 110 Ex.13 A1/10 B2/0.7 C1/0.07  100 100 Ex. 14 A1/10 B3/0.7 C1/0.07  100 100Ex. 15 A1/10 B4/0.4 C1/0.07  100 100 B1/0.3 Ex. 16 A1/10 B5/0.7 C1/0.075100 100 Comp. Ex. 1 A2/10 H1/0.7 C1/0.075 110 110

Silicon wafers were each coated with “ARC-29”, which is an organicanti-reflective coating composition available from Nissan ChemicalIndustries, Ltd., and then baked at 205° C. for 60 seconds, to form a780 Å-thick organic anti-reflective coating. Each of the photoresistcompositions prepared as above was spin-coated over the anti-reflectivecoating so that the thickness of the resulting film became 85 nm afterdrying. The silicon wafers thus coated with the respective photoresistcompositions were each prebaked on a direct hotplate at a temperatureshown in the column “PB” in Table 1 for 60 seconds. Using an ArF excimerstepper for immersion exposure (“XT: 1900Gi” manufactured by ASML,NA=1.35, 3/4 Annular, X-Y deflection), each wafer thus formed with therespective resist film was subjected to contact hole pattern exposureusing a photomask for forming a contact hole pattern having a hole pitchof 100 nm and a hole diameter of 70 nm, with the exposure quantity beingvaried stepwise.

After the exposure, each wafer was subjected to post-exposure baking ona hotplate at a temperature shown in the column “PEB” in Table 1 for 60seconds and then to paddle development for 60 seconds with an aqueoussolution of 2.38 wt % tetramethylammonium hydroxide.

Each of patterns developed on the organic anti-reflective coatingsubstrate after the development was observed with a scanning electronmicroscope, the results of which are shown in Table 2.

Effective Sensitivity (ES): It was expressed as the amount of exposurethat the hole diameter of the contact hole pattern formed using aphotomask for forming a contact hole pattern having a hole pitch of 100nm and a hole diameter of 70 nm became 55 nm.

Resolution: The photoresist pattern at ES was observed with a scanningelectron microscope. When the resolution at ES was 66 nm or less, theresolution is good and its evaluation is marked by “◯”, and when theresolution at ES was more than 66 nm, the resolution is bad and itsevaluation is marked by “X”. The resolution was shown in parentheses inTable 2. Each of the resolutions is shown in parentheses in a column of“Resolution” of Table 2.

CD uniformity (CDU): The photoresist patterns were obtained using aphotomask for forming a contact hole pattern having a hole diameter of70 nm at the exposure amount of ES. Each of patterns developed on theorganic anti-reflective coating substrate after the development wasobserved with a scanning electron microscope. The hole diameter of thecontact hole patterns was twenty four times measured and its averagediameter was calculated. The average diameters of four hundred holes onthe same wafer were respectively measured. When population was theaverage diameters of four hundred holes, the standard deviation wascalculated. When the standard deviation is less than 1.90 nm or less,CDU is very good and its evaluation is marked by “⊚”, when the standarddeviation is 1.90 nm or more and less than 2.00 nm, CDU is good and itsevaluation is marked by “◯”, and when the standard deviation is 2.00 nmor more, CDU is bad and its evaluation is marked by “X”. Further, eachof the standard deviations is also shown in parentheses in a column of“CDU” of Table 2. The smaller the standard deviation is, the better CDUthe photoresist pattern shows, and the better pattern profile is.

TABLE 2 Ex. No. Resolution CDU Ex. 11 ⊚ (65 nm) ⊚ (1.82 nm) Ex. 12 ◯ (67nm) ◯ (1.93 nm) Ex. 13 ⊚ (64 nm) ⊚ (1.78 nm) Ex. 14 ◯ (67 nm) ⊚ (1.84nm) Ex. 15 ⊚ (66 nm) ⊚ (1.80 nm) Ex. 16 ⊚ (65 nm) ⊚ (1.79 nm) Comp. Ex.1  X (70 nm)  X (2.54 nm)

Examples 17 to 22 and Comparative Example 2

<Resin>

Resin A1, A2

<Acid Generator>

Salt B6, B7, B8, B9, B10

H1:

<Quencher>C1: 2,6-diisopropylaniline<Solvent>

Y1: propylene glycol monomethyl ether acetate 265 parts propylene glycolmonomethyl ether 20 parts 2-heptanone 20 parts γ-butyrolactone 3.5 parts

The following components were mixed and dissolved, further, filtratedthrough a fluorine resin filter having pore diameter of 0.2 μm, toprepare photoresist compositions.

Resin (kind and amount are described in Table 3)

Acid Generator (kind and amount are described in Table 3)

Quencher (kind and amount are described in Table 3)

Solvent Y1

TABLE 3 Acid Resin Generator Quencher (kind/ (kind/ (kind/ amount amountamount PB PEB Ex. No. (part)) (part)) (part)) (° C.) (° C.) Ex. 17 A1/10B6/0.7 C1/0.075 100 100 Ex. 18 A2/10 B6/0.7 C1/0.075 110 110 Ex. 19A1/10 B7/0.7 C1/0.07  100 100 Ex. 20 A1/10 B8/0.7 C1/0.07  100 100 Ex.21 A1/10 B9/0.4 C1/0.07  100 100 B6/0.3 Ex. 22 A1/10 B10/0.7  C1/0.075100 100 Comp. Ex. 2 A2/10 H1/0.7 C1/0.075 110 110

Silicon wafers were each coated with “ARC-29”, which is an organicanti-reflective coating composition available from Nissan ChemicalIndustries, Ltd., and then baked at 205° C. for 60 seconds, to form a780 Å-thick organic anti-reflective coating. Each of the photoresistcompositions prepared as above was spin-coated over the anti-reflectivecoating so that the thickness of the resulting film became 85 nm afterdrying. The silicon wafers thus coated with the respective photoresistcompositions were each prebaked on a direct hotplate at a temperatureshown in the column “PB” in Table 3 for 60 seconds. Using an ArF excimerstepper for immersion exposure (“XT: 1900Gi” manufactured by ASML,NA=1.35, 3/4 Annular, X-Y deflection), each wafer thus formed with therespective resist film was subjected to contact hole pattern exposureusing a photomask for forming a contact hole pattern having a hole pitchof 100 nm and a hole diameter of 70 nm, with the exposure quantity beingvaried stepwise.

After the exposure, each wafer was subjected to post-exposure baking ona hotplate at a temperature shown in the column “PEB” in Table 3 for 60seconds and then to paddle development for 60 seconds with an aqueoussolution of 2.38 wt % tetramethylammonium hydroxide.

Each of patterns developed on the organic anti-reflective coatingsubstrate after the development was observed with a scanning electronmicroscope, the results of which are shown in Table 4.

Effective Sensitivity (ES): It was expressed as the amount of exposurethat the hole diameter of the contact hole pattern formed using aphotomask for forming a contact hole pattern having a hole pitch of 100nm and a hole diameter of 70 nm became 55 nm.

Resolution: The photoresist pattern at ES was observed with a scanningelectron microscope. When the resolution at ES was 66 nm or less, theresolution is very good and its evaluation is marked by “⊚”, when theresolution at ES was more than 66 nm and 67 nm or less, the resolutionis good and its evaluation is marked by “◯”, and when the resolution atES was more than 67 nm, the resolution is bad and its evaluation ismarked by “X”. The resolution was shown in parentheses in Table 4. Eachof the resolution is also shown in parentheses in a column of“Resolution” of Table 4

Focus margin (DOF): The photoresist patterns were obtained at theexposure amount of ES, with the focal point distance being variedstepwise. Each of contact hole patterns developed on the organicanti-reflective coating substrate after the development was observed andthe focal point distances when the contact hole patterns of which holediameter was 52.2 nm or more and 57.7 nm or less were obtained weremeasured and the difference between the max value of the focal pointdistance and the minimum value of the focal point distance wascalculated. When the difference is 0.20 μm or more, DOF is very good,and its evaluation is marked by “⊚”, when the difference is 0.17 μm ormore and less than 0.20 μm, DOF is good, and its evaluation is marked by“◯”, and when the difference is less than 0.17 μm, DOF is bad and itsevaluation is marked by “X”. Further, each of the differences is alsoshown in parentheses in a column of “DOF” of Table 4. The bigger thedifference is, the better DOF the photoresist pattern shows, and thebetter pattern profile is.

TABLE 4 Ex. No. Resolution DOF Ex. 17 ⊚ (65 nm) ⊚ (0.21 μm) Ex. 18 ◯ (67nm) ◯ (0.18 μm) Ex. 19 ⊚ (64 nm) ⊚ (0.24 μm) Ex. 20 ◯ (67 nm) ⊚ (0.18μm) Ex. 21 ⊚ (66 nm) ⊚ (0.21 μm) Ex. 22 ⊚ (65 nm) ⊚ (0.21 μm) Comp. Ex.2  X (70 nm)  X (0.03 μm)

The salt of the present invention is novel and is useful as a componentof a photoresist composition, and the photoresist composition containingthe salt of the present invention provides a photoresist pattern havinggood resolution, good CDU and good DOF, and is especially suitable forArF excimer laser lithography, KrF excimer laser lithography, ArFimmersion lithography, EUV (extreme ultraviolet) lithography, EUVimmersion lithography and EB (electron beam) lithography.

What is claimed is:
 1. A salt represented by the formula (X):

wherein Q¹ and Q² each independently represent a fluorine atom or aC1-C6 perfluoroalkyl group, L¹ and L² independently each represent aC1-C17 divalent saturated hydrocarbon group in which one or more —CH₂—can be replaced by —O— or —CO—, ring W¹ represents a C3-C36 saturatedhydrocarbon ring, R⁵ is independently in each occurrence a C1-C6 alkylgroup or a C1-C6 alkoxy group, w represents an integer of 0 to 2, vrepresents 1 or 2, Z⁺ represents an organic counter ion, and W¹⁰represents a group represented by the formula (X-1):

wherein ring W² represents a C3-C36 saturated hydrocarbon ring, R¹represents a C1-C12 hydrocarbon group, R² is independently in eachoccurrence a C1-C6 alkyl group or a C1-C6 alkoxy group, and s representsan integer of 0 to 2, or a group represented by the formula (X-2):

wherein ring W³ represents a C4-C36 lactone ring, R³ is independently ineach occurrence a C1-C6 alkyl group, a C1-C6 alkoxy group or a C2-C7alkoxycarbonyl group and t represents an integer of 0 to
 2. 2. The saltaccording to claim 1, wherein W¹⁰ is the group represented by theformula (X-1).
 3. The salt according to claim 1, wherein W¹⁰ is thegroup represented by the formula (X-2).
 4. The salt according to claim1, wherein L¹ is *—CO—O— or *—CO—O—CH₂—CO—O— in which * represents abinding position to —C(Q¹)(Q²)-.
 5. The salt according to claim 1,wherein L² is *—O—CH₂—CO—O— in which * represents a binding position toring W¹.
 6. The salt according to claim 1, wherein Z⁺ is atriarylsulfonium cation.
 7. An acid generator comprising the saltaccording to claim
 1. 8. A photoresist composition comprising the acidgenerator according to claim 7 and a resin comprising a structural unithaving an acid-labile group, being insoluble or poorly soluble in anaqueous alkali solution but becoming soluble in an aqueous alkalisolution by the action of an acid.
 9. The photoresist compositionaccording to claim 8, which further contains a basic compound.
 10. Aprocess for producing a photoresist pattern comprising the followingsteps (1) to (5): (1) a step of applying the photoresist compositionaccording to claim 8 or 9 on a substrate, (2) a step of forming aphotoresist film by conducting drying, (3) a step of exposing thephotoresist film to radiation, (4) a step of baking the exposedphotoresist film, and (5) a step of developing the baked photoresistfilm with an alkaline developer, thereby forming a photoresist pattern.